xz can take a "threads" option and if passed 0 will try and use the number of threads as the host has cpus.
In particular I noticed the arm raw images take a very long time to compress:
-rwxrwxr-x. 1 root root 4831838208 Sep 11 16:42 Fedora-LXDE-armhfp-Rawhide-20160911.n.0-sda.raw -rw-------. 1 root root 942145536 Sep 11 18:05 Fedora-LXDE-armhfp-Rawhide-20160911.n.0-sda.raw.xz (so already almost 90 minutes and still going).
but xz is only using 1 thread (the default) even though the arm builder has 4 cpus.
arm images are entirely done in appliance-creator and not in pungi.
@ausil changed the status to Invalid
Invalid
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/pungi/pungi/issues/388
Please continue any further discussion there.